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I did not know how to figure amp hours. A friend finally emailed me the info. I attached his
commentary at the bottom. CRITICAL INFO I PUT IN BOLDFACE SO YOU DON’T
HAVE TO GO THROUGH IT ALL.
And I shipped by USPS. Supposed to arrive to you tomorrow Saturday.
Please let me know how and when to pay for the reprogramming.
Thanks,
Jeffrey Gillette nakedwaterskier@yahoo.com
5735 Melvin Ave
Tarzana, CA 91356
8189160787
2002 Gem Car with Zivan Charger OEM
BMS 24 Chargery.com
Battery Chemistry Lithium with lithium-manganese-oxide nickel oxide Cathode from 2013 Nissan Leaf
Each Cell is rated at 32.5Ah OR
75V * 65Ah = 4,875 Wh = 4.875kWh. (at Nominal see below)
20 Cells x 500W = 10 kWh
Max. Cell Voltage 4.2V times 20 = 84V
Nominal Cell Voltage 3.75V times 20 = 75V
20 Cells x 500W = 10 kWh
USE ONLY 80% OF CAPACITY TO PRESERVE CYCLE LIFE
SO MAX DESIRED CELL VOLTAGE:
4V times 20 = 80V
CUT THAT TO 78V TO BE COMPATIBLE WITH GEM SYSTEM
MAX CELL VOLTAGE 3.9V times 20 = 78V
MIN CELL VOLTAGE 3.0V times 20 = 60V Please see boldface last paragraph below
The Nissan Leaf battery pack is made of 192 Lithium-Ion (LiMnO2) cells, in a 96s2p configuration.
Each cell is 32.5Ah @ 3.75V nominal, (3.2V - 4.2V). Four cells per module in a 2s2p configuration.
And with 48 modules in the pack, this results in a 65Ah @ 360V. I am using 20.
Per a Friend named David:
Amp-hours add in parallel, voltage adds in series. Volts * amps =
watts which also means that Volts * Amp-hours = Watt-hours. To
estimate the kWh of a pack the nominal voltage is typically used
though depending on the load the pack is under the actual amount of
useable energy can be different. I assume you have a string of 20 cell
pairs meaning that you have a 2p20s arrangement. If this is the case
you add the Ah of the 2 parallel cells and get 65Ah. Next you add the
nominal voltage of the cells in series which gave you the 75V figure.
75V * 65Ah = 4,875 Wh = 4.875kWh.
As for using only 80% of the cell capacity, the reserve should be at
BOTH ends of the charge/discharge curve. I don’t recall what Nissan
uses for the top and bottom end but I would start with stopping when
the cells are 95% full on charge and consider empty when there is 15%
left at the bottom end. Also, if you can have a lower cutoff point for
when you don’t need the full capacity then I would only charge to 80%
for daily use. In fact, my Kia Soul EV cuts off at about 78% actual
battery capacity when the dash says 80%. The dash only shows available
capacity to the user not the actual battery capacity so the only way I
know of to charge the battery over 95% actual SOC (state of charge) is
to charge fully at the top of a hill and then regen down the hill.
It looks like your Gem system is calibrated to 78V target voltage.
What I would do is charge to that point and then just before the
charger shuts off adjust the voltage trim pot a little to raise the
voltage a little at a time. If you turn the pot and the charger stops
charging you probably turned the pot the wrong direction. If the
charger shuts off before you are finished just restart it and it
should cut back quickly so you can continue to adjust. If it is quiet
enough and your hearing good enough you can hear a high pitched whine
from the Zivan charger when it is charging. This whine will stop and
start several times at the end of charge. This is when you want to
adjust the voltage trim pot. Adjust a little at a time so you don’t go
too far.
HTH,
David
